Ultrasonic powdered metal compaction

ABSTRACT

An apparatus for making cores for ignition coil assemblies using powdered metal having magnetically permeable material is disclosed. The apparatus includes an ultrasonic tool that includes a cavity having a first axis. The tool vibrates to provide radial compression of powdered metal placed in the cavity. The apparatus also includes a first ram and a second ram. The cavity is located between the rams; the rams are located along the first axis. The rams are configured for opposing movement toward the cavity to provide axial compression of the powdered metal placed in the cavity. The apparatus also includes a control unit that controls the operation of the ultrasonic tool and the rams, allowing for simultaneous radial and axial compression of the powdered metal for a pre-determined time into a completed core. The control unit also controls removal of the core.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] The present invention relates generally to an apparatus for producing powdered metal cores for an ignition coil, and more particularly, to the use of ultrasonic vibrations to produce powdered metal cores for an ignition coil.

[0003] 2. Description of the Related Art

[0004] In the past, ignition coil assemblies for automobile engines were placed in the engine compartment where there was sufficient space for the coil assemblies. Long wires were used to connect the coil assemblies to the spark plug assemblies. The drawbacks to this design included power losses in the wires and the inefficient amount of space used in the engine compartment. The trend is toward smaller ignition coil assemblies that can be placed close to the spark plug assembly or integrated with it. The most efficient design for these space-saving ignition coil assemblies is a cylindrical shape. However, the current methods of making the metal core for ignition coil assemblies are not entirely successful in creating cores with a sufficient density or that do not involve expensive steps in the process. One method of creating a core is uniaxially compacting powdered iron particles into cores, the particles being encapsulated individually in polymer coatings. However, with this method, the resulting cores do not have a high enough density or a uniform sufficiently density. The core center density is inadequate to provide the core with the necessary flux carrying capacity for an ignition coil. Attempts to compact the powdered iron particles in a core in a horizontal direction to improve the density of the core results in burrs created at the parting lines, which run along the width of the core. Another method of creating a core involves the use of electromagnetic compaction whereby powdered metal particles are placed in a cylinder made of conductive material, preferably copper, and the filled cylinder is placed in an electromagnetic field ranging from about 1-200 Oersted, as seen by reference to U.S. Pat. No. 6,156,264 issued to Johnston et al. Johnston et al. disclose a system wherein the magnetic field will generate eddy currents in the cylinder, which generates a counter magnetic field, thereby creating forces on the powdered iron particles that result in compaction having a uniform, high density core. In the system of Johnston et al., the cylinder serves as a pressure-transmitting medium to the powdered particles. While this process does result in a uniform, high density core, the process is expensive and requires the use of high voltages. Therefore, there exists a need to provide an apparatus that is capable of producing powdered metal cores for ignition coils that minimizes or eliminates one or more of the above deficiencies.

SUMMARY OF THE INVENTION

[0005] It is an object of the present invention to provide a solution to one or more of the above-mentioned deficiencies. In one aspect of the invention, an apparatus is provided for making ignition coil cores using a powdered metal having magnetically-permeable material. The apparatus includes an ultrasonic tool. The ultrasonic tool includes a cavity that has a first axis. Powdered metal is placed into the cavity. The tool vibrates to provide radial compression. The apparatus also includes a first and a second ram, each located along the first axis, wherein the tool cavity is located between the rams. The rams are configured for opposing movement, each toward the tool cavity, to provide axial compression of the powdered metal placed in the cavity. The apparatus further includes a means for simultaneously controlling the radial compression provided by the ultrasonic tool and the axial compression provided by the first and second rams. In one embodiment, the rams are retractable along the first axis and radially to facilitate removal of the core.

[0006] In a second aspect of the invention, a method is provided for making ignition coil cores using a powdered metal having magnetically-permeable material. The method includes the steps of providing an ultrasonic tool having a cavity that is located between a first ram and second ram. The rams are configured for opposing movement toward the cavity along a first axis. The next steps involve filling the cavity with a powdered metal and moving the rams toward each other into the cavity to compress the powdered metal. Finally, simultaneously vibrating the tool while moving the rams. In one embodiment, the rams move and the tool vibrates to aid in removal of the completed core from the cavity.

[0007] Other objects, features, and advantages of the present invention will become apparent to one skilled in the art from the following detailed description and accompanying drawings illustrating features of the this invention by way of example, but not by way of limitation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008]FIG. 1 is a simplified perspective view of an apparatus according to the invention.

[0009]FIG. 2 is a perspective view of a completed central core made using the apparatus of FIG. 1.

[0010]FIG. 3 is a flow chart of a method of making a central core according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0011] Referring now to the drawings wherein like reference numerals are used to identify identical components in the various views, FIG. 1 is a simplified perspective view of an embodiment of an apparatus 10 for making a powdered metal core. Apparatus 10 includes an ultrasonic tool 12 having a cavity 14, a first ram 16, and a second ram 18. Cavity 14, first ram 16, and second ram 18 are each located along a first axis 20. Cavity 14 is located between first ram 16 and second ram 18. First ram 16 and second ram 18 are configured for opposing movement via respective movement apparatus 21 _(a) and 21 _(b), each ram 16, 18 being capable of movement toward cavity 14. Apparatus 10 incorporates equipment including power supplies 22, 24, converters 26, 28, and boosters 30, 32 to provide the necessary mechanical power for tool 12 to ultrasonically vibrate. Apparatus 10 also includes a means, such as a control unit 34, to control operation of tool 12 and first ram 16 and second ram 18.

[0012] Apparatus 10 is used as follows. Powdered metal is placed in cavity 14. The powdered metal may be made up of magnetically permeable particles. Substantially pure iron may be used. Alternatively, iron alloys that include copper, nickel, zinc, cobalt, silicon or manganese may be used. Particle size may vary, and may range from about 5 to 400 micrometers. While not required, the particles may be encapsulated in a polymeric material. This encapsulation aids in removal of the completed metal core 39 from cavity 14. The particles must, however, be coated with an electrical insulator, polymeric or otherwise. Each particle may comprise an iron or iron alloy encapsulated in a continuous shell of an amorphous thermoplastic, thermoset and/or inorganic material, each encapsulant comprising an electrical insulator. The types of powdered metal particles and coatings may comprise those as described in U.S. Pat. No. 6,156,264 granted to Johnston, et al., assigned to Delphi Technologies, Inc., hereby incorporated by reference. Without limitation, these particles may include substantially pure iron or an iron alloy. The iron alloys that may be used include, without limitation, copper, zinc, nickel, cobalt, silicon, and manganese. The thermoplastic shell may be selected from the group consisting of a polyetherimide, polyethersulfone, and polyamideimide having a heat deflection greater than about 200° C. The thermoset shell may be selected from a group consisting of but not limited to phenolics, epoxies, alkyds, polyesters or silicones. The inorganic shell may be selected from a group consisting of but not limited to silicates, metal oxides, ceramics, borides, nitrides, carbides, ferrites, or phosphates.

[0013] Tool 12, ultrasonically vibrates radially in a plane substantially perpendicular to axis 20, providing radial compression of powdered metal. It also vibrates vertically to reduce friction so less force is required from rams 16 and 18. Tool 12 may vibrate at a preferable operating frequency of about 20 kHz and may vibrate at variable amplitudes. Power supplies 22, 24 coupled with power converters 26, 28 provide tool 12 with the mechanical power to vibrate at an ultrasonic frequency. Boosters 30, 32, resonant at the operating frequency, may be used to increase the vibration amplitude, preferably to provide a 1:3 ratio amplitude gain. Power supplies 22, 24 are controlled by control unit 34, which allows power supplies 22, 24 to operate in phase with each other. Tool 12 may comprise conventional components known to those of ordinary skill in the art. Tool 12 and power supplies 22, 24, converters 26, 28, and boosters 30, 32 may comprise commercially available components, such as a Power supplies—Branson 920 MA; Converters—Branson Model 922 JA; and Boosters—Branson part #E.O.P. 109-016-428. Tool 12 comprises an ultrasonic sonotrode.

[0014] Control unit 34 is configured to provide the means for simultaneously controlling the radial compression (i.e., ultrasonic tool 12) and the axial compression (i.e., the rams 16, 18 via apparatus 21 a and 21 b). Control unit 34 may comprise a programmed processor configured to perform the control as described herein.

[0015] The friction created by the radial vibrations of tool 12 between the inner surfaces 36 _(a), 36 _(b) of tool 12 that define cavity 14 and the powdered metal placed in cavity 14 is greatest at the axial center of cavity 14. The friction created is minimal at the axial ends 38 _(a), 38 _(b) of cavity 14. The friction created provides energy in the form of heat to aid in compressing powdered metal into an individual core 39. While tool 12 vibrates, first ram 16 and second ram 18 each move toward cavity 14 along axis 20 compressing powdered metal in axial direction. A speed range may vary and may be developed on actual equipment; but slower speeds should provide a more uniform density core.

[0016] This combination of radial and axial compression of the powdered metal, preferably simultaneously, compresses the powdered metal to a desired density within at least 96%, more preferably 99%, of the theoretical density of the powdered metal, into a core that can be advantageously used in ignition coils. As an example, iron particles bound together with 0.5% by weight of polyetherimide (i.e., ULTEM® from the General Electric Company) has a theoretical density of 7.613 g/cc. Other encapsulated powdered metals and their theoretical densities are described in U.S. Pat. No. 5,629,092 issued to Gay et al., hereby incorporated by reference. The exact amount of force required may vary and may be experimentally determined on the equipment. One major advantage of the untrasonic energy however is that it reduces drag friction on the sides of the cavity 14 and reduces friction between the particles so the force required may be significantly lower than the 50-60 tons/in² normally used for non-ultrasonic presses.

[0017] Tool 12 is of a shape such that when powdered metal is placed in cavity 14 and compressed, the resulting shape of completed core 39 is that of a cylinder. FIG. 2 illustrates a perspective view of a completed core 39 with a cylindrical shape. Tool 12 is removable from apparatus 10 and different tools could be used in apparatus 12 to produce cores of varying diameter and length, and potentially shape. Cavity 14 of tool 12 would be the determining factor in the size of the core formed.

[0018] First ram 16 and second ram 18 are adjustable in terms of respective travel along axis 20 to enable apparatus 10 to make cores of varying lengths, the limit being the axial length of tool 12. Rams 16, 18 are also controlled by control unit 34, which allows rams 16, 18 to each move toward cavity 14 along axis 20 simultaneously to compress the powdered metal located in cavity 14. Control unit 34 also controls the operation of power supplies 22, 24 (and thereby the radial, ultrasonic compression provided by tool 12). Control unit 34, by controlling both power supplies 22, 24 and rams 16, 18, controls the simultaneous axial and radial compression of the powdered metal.

[0019] Rams 16, 18 are also retractable, both along axis 20 and radially in a plane substantially perpendicular to axis 20. The retractability aids in removal of the completed core from cavity 14. By way of example, ram 18 may retract along axis 20 away from cavity 14. Further, ram 18 may be configured to retract radially so that ram 18 does not impede the removal of the core from cavity 14, inasmuch as the core is removed along axis 20. Core removal may be aided by opposing ram 16, which moves toward cavity 14 along axis 20, mirroring the movement performed when compressing powdered particles. Ram 16 may push the core out of cavity 14. Additionally, tool 12 may vibrate briefly to aid in removal of the core by loosening it within cavity 14. Control unit 34 controls operation of tool 12 and rams 16, 18 during core removal.

[0020] Referring now to FIG. 3, a method according to the invention for making a core from powdered metal of a magnetically permeable material is provided. First, tool 12 is provided 40 that has cavity 14 of whatever desired length, diameter and shape. Then, powdered metal is placed 42 in cavity 14. Rams 16, 18 then move 44 along axis 20 toward each other into cavity 14 compressing powdered metal in cavity 14. While rams 16, 18 are moving 44, tool 12 vibrates 46, aiding in compression of powdered metal, particularly the powdered metal located in the center of cavity 14. Ram moving step 44 and tool 12 vibrating step 46 are performed for a pre-determined amount of time, long enough to compress the powdered metal into a core with sufficient density to be used in ignition coils. Additional steps include removal of the core from the cavity as previously described above.

[0021] The apparatus and method of the present invention have several advantages over the known options for making powdered metal cores. First, the cores that are produced can have the desired cylindrical shape for space efficient design of ignition coil assemblies, while also having a sufficient uniform high density necessary to meet ignition coil performance requirements. Second, the apparatus used does not require use of high voltages and takes less physical space than the apparatus required for electromagnetic compression of powdered metal, making the inventive method more cost efficient. Additionally, the apparatus allows for flexibility in core sizing. Cores of different lengths and diameters can be formed because of the ease with which tool 12 and rams 16, 18 can be replaced or adjusted.

[0022] It is to be understood that the above description is merely exemplary rather than limiting in nature, the invention being limited only by the appended claims. Various modifications and changes may be made thereto by one of ordinary skill in the art which embody the principles of the invention and fall within the spirit and scope thereof. 

1. An apparatus for making cores using powdered metal having magnetically permeable material, said apparatus comprising: an ultrasonic tool, wherein said ultrasonic tool includes a cavity having a first axis, wherein said tool vibrates to provide radial compression; a first and second ram, each located along said first axis, wherein said cavity is located between said rams, said rams being configured for opposing movement toward said cavity to provide axial compression; a means for simultaneously controlling said radial compression provided by said tool and said axial compression provided by said first and second rams.
 2. The apparatus of claim 1 further comprising a respective pair of boosters and converters and a power source wherein said power source comprises two power supplies operating in phase with each other.
 3. The apparatus of claim 1 wherein said first and second rams are retractable along said first axis to facilitate removal of the completed core.
 4. The apparatus of claim 1 wherein said two rams are retractable along a second axis, wherein said second axis is substantially normal to said first axis to facilitate removal of the completed core.
 5. The apparatus of claim 1 wherein said ultrasonic tool vibrates at about 20 kHz.
 6. A method of making a core using powdered metal having magnetically permeable material, comprising the steps of: providing an ultrasonic tool having a cavity; filling said cavity with powdered metal, wherein said cavity is located between first and second rams, configured for opposing movement along a first axis; moving said rams toward each other into said cavity to compress said powdered metal; and simultaneously with said moving step, vibrating said tool.
 7. The method of claim 6 wherein said moving step and said vibrating step are performed for a pre-determined amount of time to transform said powdered metal into a completed core.
 8. The method of claim 7 further comprising the step of retracting one of said rams to facilitate removal of said core.
 9. The method of claim 8 further comprising the step of moving said ram not retracted into said cavity toward said completed core, thereby pushing said completed core from said cavity.
 10. The method of claim 8 further comprising the step of vibrating said tool to aid in removal of said core from said cavity.
 11. The method of claim 6 wherein said metal particles are selected from the group consisting of iron and iron alloys.
 12. The method of claim 7 wherein the size of said metal particles prior to compression are from about 5 to about 400 micrometers.
 13. A method of making a powdered metal core for an ignition coil comprising the steps of: providing an ultrasonic tool having a cavity; filling said cavity with powdered metal, wherein said cavity is located between first and second rams, configured for opposing movement along a first axis; moving said rams toward each other into said cavity to compress said powdered metal; simultaneously with said moving step, vibrating said tool; and removing said compressed metal core from said cavity.
 14. The powdered metal core of claim 13 wherein said powdered metal are magnetically permeable.
 15. The powdered metal core of claim 13 wherein said powdered metal is selected from the group consisting of iron and iron alloys.
 16. The powdered metal core of claim 13 wherein the particle size of said powdered metal prior to compression is from about 5 to about 400 micrometers.
 17. The powdered metal core of claim 13 wherein said removing step further comprises the step of retracting one of said rams to facilitate removal of said core.
 18. The powdered metal core of claim 17 wherein said removing step further comprises the step of moving said ram not retracted into said cavity toward said core, thereby pushing said core from said cavity.
 19. The powdered metal core of claim 18 wherein said removing step further comprises the step of vibrating said tool to aid in removal of said core from said cavity. 